Study On Seed Bank And Ecesis Process Of Seedling And Sprout Of Quercus Variabilis In Different Habitats

Quercus variabilis distributes widely in the warm temperate and the subtropical area of China is not only an important constructive species of local forest and but also a resource for tannin extracts and cork production. In order to understand the characteristics of seed bank, seed germination, the development of seedlings and sprouts and their influencing factors, 30 sampling plots belonging to different habitats in Q. variabilis forests on the north slopes of the Qinling Mountains where was the core distribution area of this species were studied. The number of Q. variabilis seeds in soil seed bank was investigated in 2008, the age structure, survival number of young seedlings and sprouts, and the growth and biomass in relation to age development were investigated during the following two years. Meanwhile, 12 environmental factors which might affect the growth of seedlings were also measured and analyzed. The main results were as follows:1. There were a great quantity of seeds in the seed bank, and the seedlings grew well. All of these had been mentioned above were the base of population regeneration. The number of intact seeds (nuts) in seed banks, being different significantly (p<0.05), were 3.60×10~3, 1.94×10~3 and 2.80×10~3 per 100 m~2 respectively among plots for understory, forest gap and forest edge. They were resulted from that the processes of remove and predation, mildewing and immaturity affected the number of seeds to different extent among the 3 kinds of habitats. While remove and predation were the main way for the loss of seeds in the 3 kinds of habitats. Few seeds were able to germinate and develop to one-year-old seedlings. Q. variabilis population had plenty of young seedlings, however, the number of seedlings decreased dramatically with the age increase. The elder seedlings might play a key role in sustained regeneration of the population. The number of seedlings, the morphological traits and biomass of seedlings in shady slop were better than those in sunny slop. With the rising of seedlings'age, the number of seedlings in forest gap was more than the number in forest edge and understory. The forest gaps which were between 150 to 200 square meters were the best habitat for the growth of seedlings, large or small gaps were not encouraged the growth significantly.2. The vegetative propagation was the supplement of the sexual reproduction. The sprouts grew quicker than the seedlings, playing a significant role in recovery. The number of sprouts of Q. variabilis in shady slop was more than that in sunny slop. At the same time, the elder sprouts'number was over than those in forest edge and understory. The growth trend of sprouts'morphological traits, biomass and the number of sprouts were similar in different habitats. The forest gaps especially middle size'gaps could experience an encouragement.3. The ratio of seedlings and sprouts are various in different habitats. The ratio of seedlings increased between the age of 1 year's old to 4 years'old, then, it declined. Shady slop, forest edge and forest gaps of middle sizes were beneficial for seedlings, therefore, there were more seedlings than other habitats. The environmental factors, such as radiation condition, air humidity, the coverage of shrub and soil moisture etc. were different in different habitats. The growth of height and biomass of the seedlings and sprouts in understory, forest gap and forest edge significant showed positive correlations with radiation condition, but was negatively correlated with air humidity soil moisture significantly, the coverage of shrub and deadwood and available nitrogen in soil. While, in the gaps of different sizes, radiation condition, air humidity soil moisture significantly, the coverage of shrub, herb and deadwood, organic matter, available nitrogen, available phosphorus, available potassium in soil were associated with the growth of seedlings and sprouts dramatically.4. Recogenizing the characteristics of sexual reproduction and vegetative propagation, regulating the ratio of these two kinds of reproduction, the population can reproduce naturally. Enclosure is the main method for regeneration and the thinning in the circle of ten years also plays an important role in population regeneration. These methods can enhance the ecological protection of Q. variabilis. Near natural forest management and thinning timely should be used. Cultivating high grade trees is one of the most important purposes of regeneration.